Alogliptin Impurity B Catalogue A164509 M.W 339.39 M.F C18H21N5O2 Specifications FAQs 3-[[6-[(3R)-3-Amino-1-piperidinyl]-3,4-dihydro-3-methyl-2,4-dioxo-1(2H)-pyrimidinyl]methyl]benzonitrile